Questions & Answers about Þetta er fyrsta beinið sem ég hafi brotið.
Why is the verb hafi in the subjunctive here instead of the normal indicative hef?
This is the subjunctive of subjective extremity. The main clause contains the exclusive word fyrsta (first). When a relative clause introduced by sem follows a superlative or an exclusive word like first, last, or only, Icelandic often uses the subjunctive to emphasize that this is a unique, extreme case from the speaker's subjective perspective.
Would it be completely wrong to use the indicative hef in this sentence?
No, it wouldn't be strictly wrong. Using the indicative hef simply states it as a dry, objective fact. However, using the subjunctive hafi is very common and natural here because it adds a subjective, personal weight to the statement, highlighting the exclusivity of it being the very first bone.
Why does bein have the definite article attached as beinið?
In English, we put the definite article before the adjective: 'the first bone'. In Icelandic, when you use ordinal numbers like fyrsti (first) or superlatives, the noun that follows takes the suffixed definite article. Therefore, it has to be fyrsta beinið (literally 'first bone-the').
Is brotið agreeing with the neuter noun beinið here?
It looks like it, but grammatically it is not! Because it follows the auxiliary verb hafa (here as hafi), brotið is in the supine form (sagnbót) to create the perfect tense. The supine never changes to agree with a noun. It just so happens that the supine in Icelandic is always identical to the neuter singular form of the past participle.